The effects of melatonin on the concentrations of inflammatory cytokines and proteins, serotonin, cortisol and melatonin in ovariohysterectomised female dogs.

Background: Ovariohysterectomy (OHE) induces inflammation and stress in female dogs. The anti-inflammatory effects of melatonin have been reported in several studies.

Objectives: The goal of this study was to assess the effects of melatonin on the concentrations of melatonin, cortisol, serotonin, α-1-acid glycoprotein (AGP), serum amyloid A (SAA), c-reactive protein (CRP), interleukin-10 (IL-10), interleukin-8 (IL-8), interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) before and after OHE.

Methods: The total number of animals was 25 and aligned in 5 groups. Fifteen dogs were divided into three groups (n = 5): melatonin, melatonin+anaesthesia and melatonin+OHE and received melatonin (0.3 mg/kg, p.o.) on days -1, 0, 1, 2 and 3. Ten dogs were assigned to the control and OHE groups (n = 5) without melatonin treatment. OHE and anaesthesia were performed on day 0. Blood samples were obtained via jugular vein on days -1, 1, 3 and 5.

Results: Melatonin and serotonin concentrations significantly increased in the melatonin, melatonin+OHE and melatonin+anaesthesia groups compared with the control group, while cortisol concentration decreased in the melatonin+OHE group compared with the OHE group. The concentrations of acute-phase proteins (APPs) and inflammatory cytokines significantly increased after OHE. The CRP, SAA and IL-10 concentrations decreased significantly in the melatonin+OHE group compared with the OHE group. The concentrations of cortisol, APPs and proinflammatory cytokines increased significantly in the melatonin+anaesthesia group compared with the melatonin group.

Conclusions: The oral administration of melatonin before and after OHE help controlling the high levels of inflammatory APPs, cytokines and cortisol induced by OHE in female dogs.